Fluid pressure producing device



Patented Mar. 29, 1938 u y UNITED STATES PATENT OFFICE PRESSUREPRODUCING DEVICE Clarence H. Bock, Detroit, Mich., assignor to i`Hydraulic Brake Company, Detroit, Mich., a

corporation of California Application December 14, 1935, SerialNo.54,507

5 Claims. (Cl. 60,-54.6)

This invention relates t fluid pressure` brake yviding a communicationbetween the cylinder and l systems and more particularly to fluidpressure the chamber, and this port is controlled by a producing devicesfor such systems. valve mechanism housed in the chamber. The Heretoforein the construction of fluid pressure cylinder also has a discharge port26 controlled producing devices havinga fluid reservoir, a cylby atwo-way valve 28. 5

inder supplied therefrom, and a piston recip- As shown, the valvemechanism for controlling rocable in the cylinder,` the cylinder hasgenerally the port 24 includes a double diametral'piston 3D beensupplied with two ports providing commureciprocable in the chamber I8and a hollow plug nications between the cylinder and the reservoir. 32threaded in the open end of the chamber hav- 10 These ports aregenerally known as the supply ing an aperture 34 providingacommunication be- 10 port and the compensating port. The latter is tweenthe chamber and the reservoir IIJ. The located slightly in advance of aflexible cup seated plug 32 receives the small end of the piston, and onthe head of the piston when the piston is in a set screw 36 in the wallof the plug limits the retracted position. Hence, when the piston ismovement of the piston.

moved on its compression stroke the pressure The piston has oppositelydisposed heads 38 15 created in thecylinder forces the wall of the cupand 40 and a projection 42 on the head 40 havinto the port and thisresults in serious injury to ing a frusto-conical end 44 adapted to seat`in the cup. The present invention aims to overthe aperture 34 in theplug 32. The body of the come this objection. piston and the projection42 are axially bored An object of the invention is to provide a comtoprovide a chamber 46 and a passage 48 com- 20 bined supply andcompensating port for a uid municating with the chamber 46, and thepassage pressure producing device. 48 communicates `with a diametralpassage 50 in `Another object of the invention is to provide a theprojection 42. u fluid pressure producing device including a res- Aleak-proof cup 52 sleeved on the projection ervoir, a cylindercommunicating therewith, a 42 and seated on the head 40 provides against25 piston reciprocable in the cylinder, and means seepage of fluid pastthe piston, and a spring 54 for control of the communication betweenrthe interposed between the plug 32 and the shoulder reservoir and thecylinder so that thel commuon the piston normally urges the pistontoward nication functions as a combined supply and comthe bottom of thechamber I8 to move the frus- 0 pensating port. f tro-conical end 44 onthe projection 42 from its 30 Other objects of the invention will appearfrom seat in the aperture 34 to establish communicathe followingdescription taken in connection tion between the reservoir I Il and thecylinder with the drawing which form a part of this spec- 22.

ification, and in which,- The passage 48 is controlled by a ap valve 5635 Fig. 1 is a schematic view of a uid pressure having a restrictedopening 58. A spring 60 35 brake system embodying the invention;interposed between the valve 56 and a ring washer Fig. 2 is a verticalsectional View of the uid 62, pressed into the open end of the chamber46, pressure producing device of the system snowing normally urges thevalve 56 to its seat, and a the positions assumed by the parts while thesysleakproof cup 64 held on the head 38 of the pisi0 tem ls underpressure; and ton by a spring 66 provides against seepage of 40 Figure 3is an enlarged view of the mechanism iluid past the piston. The valve 56with its relnterposed between the compression cylinder and Stl'iCGedOpening 58 COOpSIaCeS in the Creation 0f the reservoir showing the partsin the positions suflicient pressure beneath the piston valve 3U assumedwhen the system is not under pressure. to close this valve against theresistance of the Referring to the drawing for more specific despring 54when pressure is created in the cylin- 45 tails of the invention, IIJrepresents a reservoir der 22. having a lling'cpening I2 which may beclosed A fluid pressure delivery pipe or conduit 68 by a plug I4 havingopenings I6 for venting the suitably connected to the discharge port 26has reservoir to the atmosphere. The reservoir has branches connectedrespectively to iiuid pressure a dependent sleeve or chamber I8communicatactuated motors I0 arranged for the actuation of 50 ingtherewith and vented to the atmosphere as brakes associated with thewheels of a motor indicated at 20, the purpose of which willherevehicle. 'I'he brakes may be of conventional type inafter appear.arranged in pairs, one pair for the front wheels Acylinder 22 formednormal to the base of the of the vehicle and the other pair for therear` chamber I8 has a port 24 adjacent its head prowheels of thevehicle. 55

As shown, each of the brakes includes a fixed support or backing plate12, a rotatable drum 14 associated therewith, a pair of correspondinginterchangeable friction elements or shoes 18 pivoted on the backingplate, and a fluid pressure actuated motor corresponding to the motors10 arranged on the backing plate and operative to move the shoes intoengagement with the drum against the resistance of the retractilesprings 18 connected between the shoes.

A piston 80, reciprocable in the cylinder 22, is retained in thecylinder by a washer 82 seated on an annular shoulder in the open end ofthe cylin' der and secured in'place by a retaining ring 84 seated in agroove in the wall of the cylinder. A leakprof cup 86 seated on the headof the piston is held against displacementby a spring 88 interposedbetween the cup and the two-way valve 28. T'his vspring also serves toreturn the piston to its retracted position." A recess in the back ofthe piston receives one end of a thrust pin 92 on the other end of whichis a coupling 94 connected by a flexible boot 96 to the open end of thecylinder for the exclusionof dust and other foreign substances. Thecoupling 94 is connected by a rod 98 to a foot pedal lever |00 pivotedon a suitable support |02, and the lever is connected by a retractilespring |04 to a fixed support |06.

In operation, upon depressing the foot pedal lever |08 force istransmitted from this lever to the piston 88, resulting in moving thepiston on its compression stroke. During the initial movement of thepiston the fluid under pressure in the cylinder 22 and the chamber I8causes actuation of the piston 30 resulting in closing the port 34 andthereby cutting olf communication between the cylinder 22 and thereservoir. Upon further movement of the piston on its compression strokefluid is expelled from the cylinder 22 past the two-Way valve 28, whichinhibits retrograde movement of the fluid, and through the fluidpressure delivery pipe 68 and its branches into the fluid pressureactuated motors 10, causing actuation of the motors with the resultantspreading of the shoes 16 into engagement with the drums against theresistance of the retractile springs 18.

Upon release of the foot pedal lever |00, this lever is returned to itsnormal position under the influence of the retractile spring |04. As thefoot pedal lever moves to its retracted position, the thrust pin 92connected thereto is retracted. This results in release of the piston80, whereupon the spring 88 becomes effective to return the piston toits retracted position. Upon the initial movement of the piston on itsretraction stroke, pressure on the piston 30 is released and the pistonmoves under the influence of the spring 54 to its retracted position,resulting in opening the port 34 and thus establishing communicationbetween the cylinder 22 and the reservoir I0. Upon further movement ofthe piston on its retraction stroke, fluid is drawn from the reservoirthrough the passage 48 in the piston 30, past the valve 58 which movesdownwardly to permit free flow of fluid from the reservoir to thecylinder 22, and through port 24 into the cylinder 22.

During ,this operation fluid is returning to the cylinder 22 from themotors 'l0 under the influence of the retractile springsv'l, and whenthe cylinder is filled any fluid in excess of the quantity required tocompletely lill the cylinder is returned through the port 58 in thevalve 56, the

passage 48 in the piston, and the port I4 to the reservoir.

It will be observedl that should any expansionk or contraction of thefluid occur in the system due to changes in temperature, such expansionor contraction is readily compensated for by the flow of fluid throughthe port 58 in the valve 58.

Although this invention has been described in connection with certainspecific embodiments, the principles involved are susceptible ofnumerous other applications that will readily occur to persons skilledin the art. 'I'he invention is, therefore, to be limited only asindicated by the scope of the appended claims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is,-

1. A fluid pressure producing device comprising a reservoir, a chambercommunicating therewith, a cylinder communicating with the chamber, a

piston reciprocable in the cylinder, a piston valve reciprocable in thechamber and having a passage therethrough, a valve for control of thepassage, said last mentioned valve having a restricted openingtherethrough registering with said passage, said piston valve beingnormally positioned to provide communication between the cylinder andreservoir and being responsive to the increase of pressure in thecylinder upon advance of the piston to close such communication, andmeans for actuating the piston.

2. A iiuid pressure producing device compris- Ing a reservoir, a chambercommunicating therewith, a cylinder communicating with the chamber, apiston reciprocable in the cylinder, a piston valve in the chamber forcontrol of the communication between the reservoir and the chamber, saidpiston valve having a passage therethrough, said piston valve beingnormally positioned to provide communication between the 'reservoir andchamber but being responsive to the increase of pressure in the cylinderupon advance of the piston to close such communication, a spring pressedvalve controlling the passage in the piston valve, said spring pressedvalve having a restricted opening therethrough registering with saidpassage, and means for actuating the piston.

3. A iluid pressure producing device comprising a reservoir, a chambercommunicating therewith, a cylinder having an inlet port providingcommunication between the chamber and the reservoir and a dischargeport, a piston reciprocable ln the cylinder, a piston valve in thechamber for control of communication between the ,reservoir and chamber,said piston valve having l a passage therethrough, a spring pressedvalve for control of the passage and having a compensating port, saidpiston valve being normally positioned to open said inlet port but beingresponsive to the increase of pressure in the cylinde upon advance ofthe piston to close ythe inlet port, and means for actuating the piston.

4. A fluid pressure producing device comprising a reservoir, a chambercommunicating therewith, a cylinder having an inlet port providingcommunication between the chamber and the reservoir and an exhaust port,a piston reciprocable in the cylinder, a piston valve in the chamber forcontrol of the communication between the reservoir and the chamber andhaving a passage therethrough, a spring normally retaining the pistonvalve in inlet port opening position, a spring pressed flap valve forcontrol of the passage in the piston valve, said flap valve having acompensating port, said piston valve discharge port, a pistonreciprocable in the cylbeing responsive to the increase of pressure ininder, a piston valve in the chamber for contml the cylinder uponadvance of the piston to close of communication between the reservoirand the the inlet port, and means for actuating the pischamber andhaving a passage therethrough, a

5 to spring-pressed flap valve for control of the pas- 5 5.` A iluidpressure producing device comprissage and having a compensating port,said pising a reservoir, a chamber communicating thereton valve beingnormally in position to open said '11th. l cylinder having an inlet portproviding a inlet port but being responsive to the increase ofcommunication between the chamber and the pressure in the cylinder uponadvance of the 10 reservoir and the discharge port, a two-way valvepiston to close the inlet port, and means for ac- 10 for `control oi thedischarge port. fluid pressure tuating the piston. actuating motorsoperatively connected to the CLARENCE H. BOCK.

